Blower housing with inlet guide

ABSTRACT

A blower for a furnace is provided with an inlet guide to increase efficiency and pressure output of the blower. The blower includes a blower housing with an inlet opening and an outlet discharge opening. A cylindrical wall is provided around the inlet opening and projects into a hollow interior of the blower housing. A radial wall extends outward form the cylindrical wall toward the discharge outlet opening to prevent recirculation of gases from the outlet to the inlet during operation of the blower.

BACKGROUND OF THE INVENTION

[0001] (1) Field of the Invention

[0002] The present invention relates to a draft blower for a furnace.More specifically, the invention pertains to an improved construction ofthe blower housing for the blower where the housing has a simplified,inexpensive construction that includes an inlet guide that improves theefficiency and pressure output of the blower.

[0003] (2) Description of the Related Art

[0004] Household furnaces utilize a draft blower or inducer to drawcombustion air into a combustion chamber of the furnace where thecombustion air is mixed with fuel and ignited to produce heat for thefurnace. By the flow created by the draft blower, the combustion exhaustgases are drawn through a heat exchanger of the furnace where heat fromthe combustion exhaust gases is transferred to temperature controlledcirculating air that is circulated through the house by a main furnaceblower. The draft blower or inducer then draws the combustion exhaustgases from the heat exchanger and expels the combustion exhaust gasesinto exhaust piping that leads to the outside environment.

[0005] Generally speaking, these draft blowers or inducers are designedto provide a constant high pressure flow through the combustion chamberand heat exchanger into the exhaust piping to ensure a propercombination of combustion air with fuel to optimize burning and toensure proper heat transfer in the heat exchanger. The pressure and flowrates developed by the draft blower are a function of the blower size,blower configuration, and the speed of rotation of the blower impeller.Typically, the size of the blower is specified by the furnacemanufacturer so that the blower may fit dimensionally on the furnacewithin a predetermined envelope. Thus, the size of the impeller thatfits within an interior of the blower housing is also constrained bythese requirements. As a consequence, in order to increase the pressureoutput of a blower having a set dimensional size, the speed of rotationof the impeller must be increased. This requires outfitting the blowerwith a larger motor with increased power and design requirements. Thelarger motor often results in additional noise and increases the overallcost of the blower. Additionally, the larger blower motor also generallydecreases overall system efficiency as it requires increased powerinput.

[0006] In order to increase the pressure output of a blower withoutincreasing the rotational speed of the impeller or without utilizing alarger motor, conventional blowers use a system of baffles in the blowerhousing to direct the combustion gases drawn into the blower housing andto prevent inefficiencies from fluid recirculation or leakage within theblower housing. Conventional blowers that do not use baffles oftenexperience fluid recirculation or leakage from the exhaust outlet sideof the blower housing to the vacuum inlet side of the blower housing.This causes inefficiency in the blower that reduces the flow rate andpressure output of the blower. Baffles have been used in the prior artto prevent this recirculation and leakage. However, the baffles of theprior art generally have complex geometries that include additionalstructures such as elaborate directional vanes and surfaces added to theinterior of the blower housing that substantially alter the housing fromthe conventional volute shape of the blower housing. Thus, these bafflesmust be formed in the blower housing by additional manufacturing stepsor the baffles are added as separate parts and installed separately intothe blower housing. These added manufacturing and/or assembly stepsincrease the cost of manufacturing the blower housing.

[0007] Thus, what is needed is a blower having a blower housing with animproved construction that generates increased vacuum drawing input,increased interior flow rates and increased pressure output using aconventionally sized impeller and blower motor. Such a blower would havebaffles integrally formed in the blower housing so as to eliminatesecondary assembly operations. The baffles would be formed in a simplegeometry to allow the baffles to be formed integrally with the blowerhousing and to reduce material and eliminate costly tooling for formingthe blower housing and baffles. Additionally, such a blower housingwould have baffles that do not appreciably contribute to turbulence ornoise generated in the blower housing during operation of the blower.

SUMMARY OF THE INVENTION

[0008] The present invention overcomes the shortcomings of the prior artby providing a blower housing with an inlet guide that increases thevacuum drawing input and the pressure output of the blower housing.Preferably, the inlet guide is integrally formed with the blower housingso as to reduce assembly operations. Alternatively, the inlet guide canbe added to an existing housing by adding one or more additional parts.The inlet guide has a simple geometry that does not require complex orintricate tooling. The simple, two dimensional geometry of the inletguide reduces the material and weight of the blower housing. By formingthe inlet guide integrally with the blower housing, the cost tomanufacture the blower housing is lowered. Even when assembling theinlet guide as a separate part with the blower housing, the assembly issimplified and does not appreciably increase manufacturing costs. Theinlet guide also does not significantly contribute to the internalturbulence and noise of the blower housing during its operation.

[0009] The blower of the present invention includes a housing with adischarge outlet opening and an inlet opening with an inlet guide formedat the inlet opening. The inlet guide includes a cylindrical wall thatprojects from a peripheral edge of the inlet opening into the interiorof the blower housing. The inlet guide also includes a radial wall thatprojects axially into the blower housing interior from an end wall ofthe housing and extends radially from the cylindrical wall to the sidewall of the housing adjacent the discharge outlet opening.

[0010] The cylindrical wall and radial wall of the inlet guide directcombustion gases from the inlet opening into the blower housing interiorwhere the gases can be compressed by the impeller and expelled throughthe discharge outlet opening to exhaust piping that is vented to theatmosphere. The cylindrical wall and radial wall isolate the vacuuminlet pressure drawing a flow of air into the housing, from theincreased outlet pressure forcing the flow of combustion exhaust gasesfrom the housing. The radial wall and cylindrical wall thereby preventleakage and recirculation of combustion exhaust gases from the outletside of the blower housing to the inlet side of the blower housing.Thus, the blower housing of the present invention eliminatesinefficiencies of conventional volute blower housings with a simplified,inexpensive baffle construction.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Further objectives and features of the present invention are setforth in the following detailed description of the preferred embodimentof the invention and in the drawing figures, wherein:

[0012]FIG. 1 is a top plan view of a blower housing of the presentinvention;

[0013]FIG. 2 is a cross-sectional view of the blower housing of FIG. 1taken along line 2-2 of FIG. 1;

[0014]FIG. 3 is a top cross-sectional view of the blower housing of FIG.1 taken along line 3-3 of FIG. 2; and

[0015]FIG. 4 is a top plan view of an interior of the blower housing ofFIG. 1 with the impeller removed therefrom.

[0016] Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DETAILED DESCRIPTION OF THE INVENTION

[0017] In the foregoing discussion, the terms “top”, “bottom”, and“side” will be used for illustrative purposes to describe the parts ofthe blower and blower housing of the present invention as those partsappear and are oriented in the drawing figures. It is not intended tolimit the invention in any way through use of these terms.

[0018]FIGS. 1 and 2 show the blower of the present invention, generallyindicated at reference character 20. The blower 20 includes a housing 22with a top end wall 24 and an opposite facing bottom end wall 26. Thetop end wall 24 has opposite interior and exterior surfaces 28,30 andthe bottom end wall 26 has opposite interior and exterior surfaces 32,34where each of the top and bottom end walls 24,26 are bounded byrespective spiral shaped peripheral edges 36,38. The interior surfacesof the top and bottom walls 28,32 face each other and a volute shapedside wall 40 extends between the top and bottom end walls 24,26 at thetop and bottom end wall peripheral edges 36,38. Together the top andbottom end walls 24,26 and the side wall 40 define a hollow interior 42for the blower housing 22. Preferably, the blower housing 22 isconstructed of a high-temperature resistant plastic material capable ofbeing manufactured in high speed injection molding processes, althoughother materials, such as sheet metal, may also be used.

[0019] The blower housing hollow interior 42 is adapted to receive animpeller 44 for rotation within the blower housing interior 42.Preferably, the impeller 44 has a back plate 46 with an outer diameterD₁ and vertical impeller blades or vanes 50 arranged in a ring aroundthe impeller outer diameter D₁. The impeller vanes 50 depend from theimpeller back plate 46 and are supported by a support ring 52 oppositethe back plate 46. The support ring 52 also has an outer diameterdimension of D₁ and has a radial width dimension that corresponds to theradial width dimensions of the impeller vanes 50. This leaves a largeopening 53 through the support ring 52 that provides access to theimpeller interior, as is conventional in impeller construction.

[0020] The blower housing bottom end wall 26 is provided with a vacuuminlet opening 54 therethrough that is spaced from the peripheral edge 38of the bottom end wall. The vacuum inlet opening 54 is concentric withthe impeller 44 and is adjacent the impeller opening 53. Rotation of theimpeller 44 draws gases into the blower housing interior 42 through theinlet opening 54. Preferably, the inlet opening 54 is circular with acenter axis A-A and the impeller 44 is aligned coaxially with the inletopening center axis A-A and rotates about the inlet opening center axisA-A. Although, the drawing figures show the inlet opening 54 with agenerally circular cross section, the inlet opening 54 may have anothershape so as to be compatible with the furnace on which the blower isinstalled.

[0021] The blower housing 22 includes an outlet channel 60 formed by asemicylindrical outer wall 62 and a semicylindrical inner wall 64. Theouter wall 62 projects tangentially from both of the top and bottom endwall peripheral edges 36,38 and is an extension of the side wall 40. Theinner wall 64 is positioned opposite the outer wall 62 and merges withthe side wall 40 and the top and bottom wall peripheral edges 36,38between respective top and bottom “U”-shaped transitions 66,68. Thespiral wound side wall 40 expands radially outwardly as it extends fromthe “U”-shaped transitions 66,68 at an inlet region 70 of the blowerhousing 22 to the outlet channel outer wall 62. The outlet channel outerwall 62 merges with the side wall 40 at the outermost expansion of theside wall 40, and the outlet channel inner wall 64 connects to the sidewall 40 at the “U”-shaped transitions 66,68. Rotation of the impeller 44in a counterclockwise direction as viewed in FIG. 3 creates a vacuumthat draws exhaust gases through the inlet opening 54 and into thehousing interior 42 and compresses the gases in the housing interior 42before forcing the pressurized gases from the blower housing through theoutlet channel 60 and its outlet discharge opening 72.

[0022] Preferably, the blower housing 22 is formed as two pieces whichare interlocked together to enclose and seal the blower housing hollowinterior 42. As shown in the Figures, the blower housing 22 of thepresent invention is formed with a top piece 80 and matching bottompiece 82 that assemble together to form an integral unit of the blowerhousing 22. In this arrangement, the top piece 80 preferably includesthe top end wall 24, a portion of the side wall 40, and a portion of theoutlet channel 60. Similarly, the bottom piece 82 includes the bottomend wall 26, a portion of the side wall 40, and a portion of the outletchannel 60. As shown in the Figures, the bottom piece 82 is formed witha sealing lip 84 and the top piece 80 is formed with a matching sealinggroove 86 where the lip 84 is received in the groove 86 to lock the topand bottom pieces 80,82 together. To maintain the sealed blower housinginterior 42 at the interface of the top and bottom pieces 80,82,matching engagement pads 88 are provided. The engagement pads 88 arecircumferentialy spaced about the side wall and extend outward from theside wall 40. Each of the engagement pads 88 has a fastener hole 90therethrough and a mechanical fastener (not shown) is directed throughthe hole 90 to secure the top and bottom pieces 80,82 together. Othermeans may be employed to secure the top and bottom pieces together, forexample adhesives.

[0023] In the preferred embodiment of the invention, the top end wall 24is provided with a plurality of screw connections 92 that allow a blowermotor (not shown) to be secured to the blower housing 22. The top endwall 24 is also formed with a blower motor shaft hole 94. A blower motorshaft 96 extends from the blower motor (not shown) through the blowermotor shaft hole 94 into the blower housing hollow interior 42 where itis coupled to the impeller back plate 46. Preferably, the shaft hole 94and the inlet opening 54 are coaxially aligned along the inlet openingcenter axis A-A. In this configuration, the bottom end wall 26 is formedwith the inlet opening 54 axially opposite the blower motor shaft hole94.

[0024] In order to minimize piping connections in the furnace, theblower housing inlet opening 54 is preferably directly aligned with anoutlet of the furnace, or furnace bonnet (not shown), where thecombustion gases exit the heat exchanger (not shown) of the furnace. Inorder to secure the blower housing 22 to the furnace bonnet (not shown),mounting pads 98 are preferably provided on the coterminous edge of theside wall 40 and the bottom end wall 26 and are circumferentialy spacedabout the spiral wound side wall 40 extending outward from the side wall40.

[0025] As shown in the Figures, the inlet opening 54 has a peripheraledge 100 and a cylindrical wall 102 extends around the inlet openingcenter axis A-A and projects axially into the blower housing interior 42at the inlet opening peripheral edge 100. Although the drawing figuresshow the cylindrical wall 102 as having a generally circularcross-section that is consistent with the geometry of the inlet opening54, the cylindrical wall 102 may have a shape other than a cylinder soas to match the general shape of the inlet opening 54 and form a smoothtransition therewith. The cylindrical wall 102 has a smooth interiorbore 104 with an inner diameter dimension D₂. In the preferredembodiment, the inner diameter dimension D₂ is less than half of aninterior dimension of the housing measured across the housing from the“U”-shaped transition 68, across the inlet open center axis A-A to theopposite side of the housing 22. The bore 104 is preferably alignedconcentric with the impeller 44. The cylindrical wall 102 has an outersurface 108 with an outer diameter dimension D₃. To provide radialsupport for the cylindrical wall 102, a support wall 112 is formedaround the outer surface 108 of the cylindrical wall 102 and the bottomend wall interior surface 32. The support wall 112 has a smaller axialheight dimension than the cylindrical wall 102 so that the support wall112 does not interfere with the flow of exhaust gases drawn into theblower housing interior 42 through the bore 104 of the cylindrical wall102.

[0026] The bottom end wall 26 of the blower housing 22 is provided witha radial wall 114 that projects axially from the bottom end wallinterior surface 32 and extends radially from the cylindrical wall outersurface 108 to the “U”-shaped transition 68. Preferably, the radial wall114 is a planar member that projects perpendicularly from the bottomwall interior surface 32 so as to simplify the shape of the housingbottom piece 82 and to allow simplified molding of the bottom end wall26 and the radial wall 114. Preferably, the radial wall 114 defines aplane that also includes the inlet opening center axis A-A. In thisarrangement, the radial wall 114 connects to the side wall 40 at theposition in the blower housing interior where the radial clearancebetween the impeller 44 and the side wall 40 is the smallest. At thisposition, the potential for fluid flow crossing from the outlet channel60 of the blower housing to the inlet region 70 of the blower housing 22is the highest. By aligning the radial wall in a plane that includes theinlet opening center axis, the flow of exhaust gases exiting the blowerhousing is directed by the radial wall 114 toward the discharge outletopening 72. In addition, the angles between the radial wall 114 and theouter surface 108 of the cylindrical wall 102 are both equal and aremaximized, which simplifies the removal of the mold (not shown) from themolded radial wall 114 and cylindrical wall 102 of the housing.Preferably, the axial height of the cylindrical wall 102 and the radialwall 114 are the same so as to minimize turbulence within the blowerhousing interior 42 and also to simplify molding and the removal of themold from the walls. For example, if the cylindrical wall were higherthan the radial wall it may have a tendency to stick in the mold makingremoval of the blower housing difficult. The axial height of the radialwall 114 is such that when the impeller 44 is installed in the blowerhousing interior 42, the impeller support ring 52 has an axial clearanceabove the radial wall 114 that permits free rotation of the impeller 44in the blower housing hollow interior 42. This also axially spaces theimpeller 44 from the cylindrical wall 102. Preferably, the housingbottom piece 82, cylindrical wall 102, support wall 112, and radial wall114 are integrally formed. More preferably, the bottom piece 82,cylindrical wall 102, support wall 112, and radial wall 114 are formedmonolithically by molding them as one piece.

[0027] During operation of the blower 20, exhaust and combustion gasesare drawn through the inlet opening 54 and through the cylindrical wallbore 104 into the blower housing hollow interior 42 by a vacuum createdin the impeller interior by rotation of the impeller 44. As the inletopening and cylindrical wall inner diameter D₂ is smaller than theimpeller outer diameter D₁, the combustion gases are expanded radiallyoutward in the blower housing interior 42 as they flow from thecylindrical wall 102 through the vanes 50 to the outer diameter D₁ ofthe impeller. By sizing the inlet opening 54 and cylindrical wall innerdiameter D₂ with a smaller dimension than the impeller outer diameterD₁, a stronger vacuum drawing pressure is formed in the blower housing22. This enables a blower 20 with a standard impeller to develop higherflow rates and increased outlet pressures. Preferably, the impeller 44used in the blower 20 has an outer diameter dimension D₁ that is atleast twice as large as the inner diameter D₂ of the cylindrical wall102 and preferably is between 4¾ inches and 5 inches and has an axialheight between 1.700 inches and 1.900 inches, and, preferably, thecylindrical wall outer diameter dimension D₃ is between 1⅞ inches and 2⅛inches, and with a tube wall dimension of between {fraction (7/32)}inches and {fraction (9/32)} inches, the bore inner diameter D₂ isroughly 1⅝ inches to 2 inches. The inventor has found that the sizes anddimensions stated herein provide the most effective combination formaximizing the flow characteristics of the blower. As will be apparentto those skilled in the art, other sizes and dimensions of components ofthe blower may also be used in accordance with the general principles ofthe invention.

[0028] The rotation of the impeller 44 compresses the combustion exhaustgases as it forces a flow of the gases counterclockwise around theblower housing interior 42 as viewed in FIG. 3 and expels the combustionexhaust gases through the outlet channel 60 and the outlet dischargeopening 72. The radial wall 114 provided in the bottom end wall 26prevents combustion exhaust gases from recirculating from the outletchannel 60 across the area adjacent the “U”-shaped transitions 66,68 tothe inlet region 70 of the blower housing 22. This creates a moreefficient flow within the blower housing interior 42 and enables ablower 20 with a set impeller diameter and a set impeller rotationalspeed to develop increased output pressure and flow rates. In order tominimize recirculation of exhaust gases from the outlet channel 60 backtoward the blower housing inlet region 70 along the top wall end 24, thetop end wall 24 is preferably formed flat in a plane perpendicular tothe inlet opening center axis A-A and the impeller back plate 46 ispositioned with minimal axial clearance between it and the top end wall24.

[0029] As will be apparent to those skilled in the art, the inlet guide,including the cylindrical wall 102 and the radial wall 104 describedherein, is of a simple geometry that facilitates the manufacturing ofthe blower housing 22. Thus, the blower housing 22 may be formed fromsimple molding processes that do not require sophisticated tooling withintricate surfaces or tooling that requires die inserts. Moreover, theinlet guide described herein may also be retrofitted into existingblower housings by securing the cylindrical wall 102 and radial wall 114to the housing interior at the inlet opening 54. For example, a blowerhousing may be retrofit with the inlet guide described herein bysecuring a section of tubing, such as a PVC pipe, within the existinginlet opening of the blower housing so that it extends a short distanceinto the blower housing interior. The pipe section may also be attachedto the interior surface of the bottom end wall such that the bore of thepipe section matches the inlet opening. A section of flat stock may thenbe used to form the radial wall in the manner described previously. Inaddition to forming the blower housing from a plastic material, theblower housing may also be constructed from sheet metal in which casethe inlet guide may be similarly constructed and joined to the blowerhousing using metal joining techniques common in the art, i.e. welding,brazing, clinch joints, mechanical fasteners, adhesives.

[0030] While the present invention has been described by reference tospecific embodiments, it should be understood that modifications andvariations of the invention may be constructed without departing fromthe scope of the invention as defined by the following claims.

What is claimed:
 1. A housing for a furnace blower, the housingcomprising: a housing end wall having opposite interior and exteriorsurfaces and a peripheral edge with a volute shape, an inlet openingthrough the end wall spaced from the peripheral edge, and an outletchannel having opposite inner and outer walls with the outer wallprojecting tangentially from the end wall peripheral edge and the innerwall merging with the peripheral edge through a “U”-shaped transition;and a cylindrical wall extending around a center axis of the inletopening and projecting axially from the end wall interior surface, thecylindrical wall having an interior diameter dimension that is less thanhalf of an interior dimension of the housing measured across the endwall from the “U”-shaped transition, across the inlet opening centeraxis to the end wall peripheral edge opposite the center axis from the“U”-shaped transition.
 2. The housing of claim 1, wherein: the inletopening is circular and the inlet opening and the cylindrical wall haveinterior diameter dimensions that are equivalent.
 3. The housing ofclaim 1, wherein: a radial wall projects axially from the end wallinterior surface and extends between the cylindrical wall and the“U”-shaped transition.
 4. The housing of claim 3, wherein: thecylindrical wall and the radial wall have axial dimensions that areequivalent.
 5. The housing of claim 3, wherein: the radial wall is astraight wall.
 6. The housing of claim 3, wherein: the radial wall ispositioned in a plane that also contains the inlet opening center axis.7. The housing of claim 3, wherein: the cylindrical wall and the radialwall are integrally connected to each other and are integrally connectedto the end wall interior surface and the “U”-shaped transition.
 8. Thehousing of claim 3, wherein: the cylindrical wall, the radial wall, andthe housing end wall are one monolithic piece.
 9. The housing of claim1, wherein: an impeller is mounted for rotation in the housing and isaxially spaced from the cylindrical wall.
 10. A housing for a furnaceblower, the housing comprising: a housing end wall having oppositeinterior and exterior surfaces and a peripheral edge that spirals aroundthe end wall, an inlet opening through the end wall spaced from theperipheral edge, and an outlet channel having opposite inner and outerwalls with the outer wall projecting tangentially from the end wallperipheral edge and the inner wall merging with the peripheral edgethrough a “U”-shaped transition; a cylindrical wall extending around acenter axis of the inlet opening and projecting axially from the endwall interior surface, the cylindrical wall having a diameter dimension;and an impeller mounted for rotation in the housing around the inletopening center axis and the cylindrical wall, the impeller having adiameter dimension that is at least twice as large as the cylindricalwall diameter dimension.
 11. The housing of claim 10, wherein: theimpeller outer diameter dimension ranges from 4¾″ and 5″ and thecylindrical wall outer diameter dimensions ranges from 1⅞″ and 2⅛″. 12.The housing of claim 11, wherein: the impeller has an axial height ofbetween 1.700″ and 1.900″.
 13. The housing of claim 10, wherein: aradial wall projects axially from the end wall interior surface andextends between the cylindrical wall and the “U”-shaped transition. 14.The housing of claim 13, wherein: the cylindrical wall and the radialwall have axial dimensions that are equivalent.
 15. The housing of claim14, wherein: the cylindrical wall, the radial wall, and the end wall areone monolithic piece.
 16. The housing of claim 10, wherein: the impelleris axially spaced from the cylindrical wall.
 17. A housing for a furnaceblower, the housing comprising: a housing first end wall having oppositeinterior and exterior surfaces and a peripheral edge that spirals aroundthe first end wall, an inlet opening having a center axis passingthrough the first end wall, and an outlet channel having opposite innerand outer walls with the outlet channel outer wall projectingtangentially from the peripheral edge and the outlet channel inner wallmerging with the peripheral edge through a “U”-shaped transition; ahousing second end wall having opposite interior and exterior surfacesand a peripheral edge that spirals around the second end wall, a shaftopening coaxial with the inlet opening passing through the second endwall, and an outlet channel having opposite inner and outer walls withthe outer wall projecting tangentially from the peripheral edge and theinner wall merging with the peripheral edge through a “U”-shapedtransition; a sidewall connecting the peripheral edge of the first endwall with the peripheral edge of the second end wall and together withthe first and second end walls defining a hollow interior of thehousing; and an impeller mounted for rotation in the hollow interior ofthe housing, the impeller having first and second annular walls adjacentthe respective first and second end walls, and portions of the first andsecond end walls that are adjacent the impeller first and second annularwalls are entirely planar.
 18. The housing of claim 17, wherein: aradial wall projects axially from the first end wall interior surfaceand extends between the cylindrical wall and the “U”-shaped transitionof the first end wall.
 19. The housing of claim 18, wherein: thecylindrical wall and the radial wall have axial dimensions that areequivalent.
 20. The housing of claim 17, wherein: the cylindrical wallhas an outside diameter dimension and the impeller has an outsidediameter dimension that is at least twice as large as the cylindricalwall outside diameter dimension.